Usually,’ frogs’ teeth aren’t anything to make a fuss about, they look like pointed little pinpricks lining the upper jaw. But one cluster of stream-dwelling frogs in Southeast Asia has a bizarre adaptation: two bony “fangs” projecting out of their lower jawbone. They use these fangs to fight with each other over terrain and mates, and occasionally even to hunt tough-shelled prey like giant centipedes and crabs. In a new study, available in the journal PLOS ONE, scientists have labelled a new species of fanged frog: the smallest one ever discovered.
This new species is tiny related to other fanged frogs on the island where it was found, around the size of a quarter, says Jeff Frederick, a postdoctoral scholar at the Field Museum in Chicago and the study’s lead author, who led the research as a doctoral candidate.
Many frogs in this species are giant, weighing up to two pounds. At the large end, this novel species weighs about the same as a dime.
In partnership with the Bogor Zoology Museum, a team from the McGuire Lab located the frogs on Sulawesi, a rocky, mountainous island that makes up part of Indonesia.
It’s a massive island with a vast web of mountains, volcanoes, lowland rainforest, and cloud forests high up in the mountains. The existence of all these diverse habitats means that the extent of biodiversity across many plants and animals we find there is unreal — equaling places like the Amazon, says Frederick.
While hiking through the jungle, members of the joint US-Indonesia amphibian and reptile research team observed something surprising on the leaves of tree saplings and moss-covered stones: a clutch of frog eggs.
Frogs are amphibians, and they lay eggs that are compressed by jelly, rather than a hard, defensive shell.
To preserve their eggs from drying out, most amphibians lay their eggs in water.
To the investigating team’s astonishment, they kept detection the terrestrial egg masses on leaves and mossy stones several feet above the ground.
Soon after, they began to see the small, brown frogs themselves.
Usually when we’re looking for frogs, we’re skimming the margins of stream banks or wading through streams to spot them straight in the water, Frederick says.
After recurrently monitoring the nests though, the team started to find attending frogs sitting on leaves caressing their little nests. This close interaction with their eggs permits the frog parents to coat the eggs with mixtures that keep them moist and free from bacterial and fungal infection.
Closer inspection of the amphibian parents discovered not only that they were tiny associates of the fanged frog family, complete with barely-visible fangs, but that the frogs caring for the nest of eggs were all male.
Male egg protecting behavior isn’t completely unknown across all frogs, but it’s rather rare, says Frederick.
Frederick and his colleagues theorized that the frogs’ uncommon reproductive manners might also relate to their smaller-than-usual fangs.
Some of the frogs’ relatives have larger fangs, which assist them ward off rivalry for spots along the river to lay their eggs in the water.
Since these frogs advanced a way to lay their eggs away from the water, they may have lost the necessity for such big impressive fangs.
(The scientific name for the new species is Limnonectes phyllofolia; phyllofolia means “leaf-nester.”)
It’s captivating that on every succeeding expedition to Sulawesi, we’re still discovering new and assorted reproductive modes, says Frederick. The results also underline the importance of preserving these very distinct tropical habitats. Most of the animals that live in settings like Sulawesi are fairly unique, and habitat destruction is an ever-looming preservation issue for conserving the hyper-diversity of species we find there. Learning about animals like these frogs that originate nowhere else on Earth helps make the situation for protecting these valuable ecosystems.
